1. Field of the Invention
The present invention relates to liquid printers, and more particularly, to a liquid printer having a carrier vapor diluting unit which dilutes and exhausts carrier vapor generated in a fusing apparatus to fuse an image on paper using heat and pressure.
2. Description of the Related Art
In general, liquid printers form a toner image by supplying a developing agent in which toner particles are distributed to a liquid carrier, to an electrostatic latent image formed on a photosensitive body and transfer the toner image onto paper, fuse the toner image on the paper and form an image.
FIG. 1 schematically shows a conventional liquid printer using a low-concentration developing agent having a toner concentration of 2.5-3% solid. Referring to FIG. 1, the conventional liquid printer includes a photosensitive belt 20 charged to a predetermined voltage by a charger 10, a light scanning unit 40 which forms an electrostatic latent image of a desired image by irradiating light on the charged photosensitive belt 20 and forming a relative potential difference between a portion on which light is irradiated and a portion on which light is not irradiated, a developing unit 30 which forms a toner image on the photosensitive belt 20 by supplying a developing agent to the electrostatic latent image, a transfer roller 60 which transfers the toner image developed on the photosensitive belt 20 onto paper S, and a fusing roller 70 which fuses the toner image on the paper S using heat and pressure.
In a liquid printer, ink having high concentration of about 12% solid is withdrawn from an ink reservoir 34, and ink is mixed and diluted by a mixer 35 with a liquid carrier supplied from a carrier reservoir 37, and ink is formed as a low-concentration developing agent having toner concentration of 2.5-3% solid and is then supplied to a developing container 33 using a pump 36.
To develop an electrostatic latent image using a low-concentration of the developing agent, sufficient toner should be supplied to the electrostatic latent image. Thus, in the liquid printer shown in FIG. 1, a sufficient developing agent is spread between the photosensitive belt 20 and a developing roller 31, and an excessively-spread developing agent is removed using a squeeze roller 32.
Before the toner image formed on the photosensitive belt 20 is transferred onto the transfer roller 60, a drying process to remove a liquid carrier attached to the photosensitive belt 20 liquid carrier for the toner is performed. For this purpose, a drier 50 is installed between the developing unit 30 and the transfer roller 60. The drier 50 evaporates the liquid carrier by spreading the high-temperature air on the photosensitive belt 20 and transfers a mixed gas in which carrier vapor is mixed with the air, to a condenser 80. After the drying process is performed, the toner image formed on the photosensitive belt 20 is transferred to the transfer roller 60.
A fusing roller 70 is engaged with the transfer roller 60 and rotates, and the paper S is transferred between the fusing roller 70 and the transfer roller 60. Then, the toner image is transferred onto the paper S and is fused on the paper S due to the heat and pressure generated in the transfer roller 60 and the fusing roller 70. A transfer roller cleaning unit 61 is provided in the transfer roller 60. The transfer roller cleaning unit 61 evaporates the liquid carrier remaining in the transfer roller 60 and transfers the mixed gas in which the carrier vapor is mixed with the air, to the condenser 80.
The condenser 80 withdraws the liquid carrier by condensing the mixed gas transferred by the drier 50 and the transfer roller cleaning unit 61. The mixed gas passes through the condenser 80, and the liquid carrier is filtered again while passing through the filter 90, and is exhausted to the air.
Likewise, the liquid printer using a low-concentration developing agent includes a plurality of heat sources such as the drier 50, the transfer roller cleaning unit 61, and the fusing roller 70, and thus, a large amount of carrier vapor is generated in the liquid printer. Thus, in order to withdraw carrier vapor, the condenser 80, the filter 90, and pipes 81 and 82 to connect the condenser 80 to the filter 90, and a fan (not shown) to transfer the mixed gas forcibly to the condenser 80 are provided.
However, a liquid printer which may be used without diluting a high-concentration developing agent having a toner concentration over 3% solid has been recently suggested. A process to dilute high-concentration ink is not needed in the liquid printer. Thus, the liquid printer does not require the mixer 35, the pump 36, and the squeeze roller 32, and has a simplified and compact structure. In addition, since a heat source is not used, excluding in a process for fusing the toner image on the paper S using heat, the amount of carrier vapor is smaller than the amount of carrier vapor in a liquid printer using a low-concentration developing agent. Thus, a method to mix carrier vapor with the air and dilute and exhaust the carrier vapor, rather than withdraw the carrier vapor using a complicated apparatus such as the condenser 80 of FIG. 1, is required.